Nickel is an important industrial metal and end-uses of the metal include stainless steels, high temperature alloys such as Inconel (Registered Trade Mark), and catalysts.
The nickel-containing ore may be any ore, such as an oxide ore, i.e. a laterite ore, or a sulphide ore.
Nickel intermediate products include, by way of example, nickel carbonates as produced by the Caron process at the Yabulu refinery of the applicant.
Nickel intermediate products also include, by way of example, nickel hydroxide products, or nickel oxide products.
The present invention relates particularly, although by no means exclusively, to the production of nickel from a nickel intermediate product in the form of a nickel hydroxide product, that is produced by hydrometallurgically processing a nickel-containing ore or a concentrate of the ore. Preferably, the nickel hydroxide product is subjected to further processing comprising drying and/or calcination to remove water prior to use.
The term “nickel hydroxide product” is understood herein to mean any product that contains nickel hydroxide that is produced by hydrometallurgically processing a nickel-containing ore or a concentrate of the ore and includes products that also contain other compounds such as any one or more of iron hydroxides, magnesium sulphates, calcium sulphates, manganese oxides and/or hydroxides, cobalt hydroxides, alumina, silica, and sodium sulphates and trace amounts of other elements.
Typically, when produced by hydrometallurgical processing, the nickel hydroxide product is in the form of a paste or a slurry with a water (i.e. moisture) content of 30-75 wt %. It also typically includes sulphur when the product is derived from a hydrometallurgical process which included sulphuric acid leaching. In any given situation, the water content depends on a range of factors, including the particle size distribution of the solid components, the degree of mechanical filtration or de-watering, and evaporation. Prior to its use in the process of the present invention, it is preferable to substantially remove free water and water of crystalisation, in addition to any sulphur, from the nickel hydroxide product.
The nickel hydroxide product may be produced by (a) any suitable hydrometallurgical process (such as pressure acid leaching, heap leaching under acidic conditions, and atmospheric acid leaching—or a combination) that brings nickel into an aqueous solution and (b) precipitating nickel hydroxide from solution for example using compounds such as MgO, CaO, CaCO3, and Na2CO3.
One particular example of a hydrometallurgical process is a process that comprises extracting nickel and iron from an aqueous solution onto an ion exchange resin, stripping the nickel and iron from the resin with an acid and forming another aqueous solution, and then precipitating nickel and iron as a nickel iron hydroxide product.